Re: core dumps in auto_prewarm, tests succeed

On Mon, Jan 22, 2024 at 02:44:57PM -0600, Nathan Bossart wrote:
> On Mon, Jan 22, 2024 at 12:41:17PM -0800, Andres Freund wrote:
>> I noticed that I was getting core dumps while executing the tests, without the
>> tests failing. Backtraces are vriations of this:
>
> Looking, thanks for the heads-up.

I think this is because the autoprewarm state was moved to a DSM segment,
and DSM segments are detached before the on_shmem_exit callbacks are called
during process exit. Moving apw_detach_shmem to the before_shmem_exit list
seems to resolve the crashes.

diff --git a/contrib/pg_prewarm/autoprewarm.c b/contrib/pg_prewarm/autoprewarm.c
index 9ea6c2252a..88c3a04109 100644
--- a/contrib/pg_prewarm/autoprewarm.c
+++ b/contrib/pg_prewarm/autoprewarm.c
@@ -165,7 +165,7 @@ autoprewarm_main(Datum main_arg)
first_time = false;

/* Set on-detach hook so that our PID will be cleared on exit. */
- on_shmem_exit(apw_detach_shmem, 0);
+ before_shmem_exit(apw_detach_shmem, 0);

/*
* Store our PID in the shared memory area --- unless there's already

--
Nathan Bossart
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